diff --git a/builder/build.sh b/builder/build.sh
index eaae21d..8559eaf 100755
--- a/builder/build.sh
+++ b/builder/build.sh
@@ -2,9 +2,6 @@
 
 # Build a container using the spec file provided
 
-START_DIR=$PWD
-cd "$(dirname "$BASH_SOURCE[0]}")"
-
 help_msg(){
     echo "Usage: $0 [specfile] [tag]"
     echo
@@ -40,14 +37,14 @@ fetch_packages(){
 }
 
 build_container(){
-    docker build -t $1 -f "Dockerfile" "$START_DIR/build"
+    docker build -t $1 -f "$(dirname $0)/Dockerfile" "$PWD/build"
 }
 
 
-SPEC_FILE=$START_DIR/$1
+SPEC_FILE=$1
 TAG=$2
 
-[ -z "$1" ] && help_msg "specfile is required"
+[ -z "$SPEC_FILE" ] && help_msg "specfile is required"
 [ -z "$TAG" ] && help_msg "tag is required"
 
 [ -f "$SPEC_FILE" ] || help_msg "specfile does not exist"
@@ -61,4 +58,4 @@ fetch_packages $SPEC_FILE
 build_container $TAG
 
 echo "Start your custom piston container with"
-echo "$ docker run --tmpfs /piston/jobs -dit -p 2000:2000 $TAG"
+echo "$ docker run --tmpfs /piston/jobs -dit -p 2000:2000 $TAG"
\ No newline at end of file